MTC device and communication method of said MTC device

Abstract

The purpose of the present invention is to provide an MTC device capable of improving the stability of communication quality in machine communication, and a communication method of said MTC device.　This MTC device (10) performs wireless communication with a core network (CN) via a base station (BS). The MTC device (10) comprises: a communication module (12) capable of transitioning between an attached state in which the communication module (12) can communicate with the core network (CN) and a detached state in which the communication module (12) cannot communicate with the core network (CN); and a control module (15) that controls the communication module (12). The control module (15) acquires a communication status with which it is possible to assess whether the communication module (12) is in the attached state or the detached state, and, in cases where the communication module (12) is assessed to be in the detached state on the basis of the communication status, controls the communication module (12) so as to be attached to the core network CN.

Description

MTC Device and Communication Method of the MTC Device , ,

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[0001] The present invention relates to an MTC device and a communication method of the MTC device, and particularly relates to an MTC device that communicates with a core network via a base station and a communication method of the MTC device.

[0002] In recent years, with the spread of the IoT, machine communication systems equipped with MTC (Machine Type Communication) devices that communicate between devices have become widespread. In particular, machine communication systems using cellular communication lines having a wide communication area have attracted attention. A cellular communication line divides a communication area into a certain section (cell), and a base station is arranged in each cell. In other words, an MTC device can perform wide-area communication by communicating with a core network (the core part of the network) via base stations distributed in cells.

[0003] Here, an upper limit is defined for the number of communication terminals that can communicate with one base station. Therefore, when the number of communication terminals located in a cell does not exceed the upper limit, the communication terminals are maintained in an attach state (online state) capable of communicating with the core network. On the other hand, when there are communication terminals exceeding the upper limit in a cell, some communication terminals are controlled to be in a detach state. The detach state is an offline state in which a communication terminal cannot communicate with a base station and a core network. Patent Document 1 describes a service capability server that can forcibly control an MTC device to be in a detach state when a predetermined event occurs in the MTC device.

[0004] Japanese Patent Translation of PCT International Publication No. 2016-506694

[0005] As described above, machine-to-machine communication can be realized in a wide communication area by a machine communication system using a cellular communication line. However, due to the influence of the communication environment within the cell covered by the base station, an MTC device may be controlled to be in a detach state, thereby losing the communication opportunity of the MTC device and making it difficult to ensure stable communication quality in some cases.

[0006] The present invention has been made in view of the above-mentioned problems, and the object of the present invention is to provide an MTC device capable of improving the stability of communication quality in machine communication, and a communication method for the MTC device.

[0007] The aforementioned problems are solved by the MTC device of the present invention, which is a Machine Type Communication (MTC) device that performs wireless communication with a core network via a base station, comprising: a communication module that can transition between an attached state in which communication with the core network is possible and a detached state in which communication with the core network is impossible; and a control processor that controls the communication module, wherein the control processor acquires a communication status that can determine the attached state and the detached state of the communication module, and controls the communication module to attach to the core network when it is determined that the communication module is in a detached state based on the communication status.

[0008] According to the above configuration, the MTC device includes a communication module that communicates with the core network via a base station, and a control processor that controls the communication module. The control processor acquires a communication status that allows it to determine the attached and detached states of the communication module, and controls the communication module to attach to the core network when it is determined to be in a detached state. Therefore, when the communication module is controlled to a detached state due to the influence of the communication environment within the cell, the control processor can control the communication module to attach to the core network. This makes it possible to suppress the loss of communication opportunities for the MTC device and improve the stability of communication quality in machine communication.

[0009] Furthermore, the control processor controls the MTC device so that it transitions between a first operating state in which the MTC device operates with a first power energy and a second operating state in which the MTC device operates with a second power energy smaller than the first power energy. The communication module communicates with the core network in the first operating state, and the control processor acquires the communication status in the second operating state. According to the above configuration, the control processor controls the MTC device so that it transitions between a first operating state in which the MTC device operates with a first power energy and a second operating state in which it operates with a second power energy smaller than the first power energy, and acquires the communication status in the second operating state. Therefore, the control processor can monitor the attached and detached states of the communication module while suppressing the increase in power consumption associated with the monitoring.

[0010] Furthermore, the communication module and the control processor are connected to each other via a plurality of communication ports, and the control processor may obtain the communication status from the communication module via a dedicated communication port among the plurality of communication ports. With the above configuration, since the control processor obtains the communication status via a dedicated communication port, it becomes possible to monitor the attached and detached states of the communication module without affecting the communication between the control processor and the communication module.

[0011] Furthermore, the dedicated communication port is preferably a communication port compatible with the GPIO (General Purpose Input / Output) interface. With the above configuration, the control processor communicates with the communication module via the GPIO interface-compatible communication port, thereby suppressing the increase in power consumption associated with communication and reducing the cost of the MTC device.

[0012] Furthermore, the aforementioned problems are solved by the communication method of the present invention, which is a communication method for an MTC (Machine Type Communication) device that performs wireless communication with a core network via a base station, and which acquires a communication status that can determine the attached state and detached state of a communication module that can transition between an attached state in which communication with the core network is possible and a detached state in which communication with the core network is not possible, without going through the base station, and controls the communication module without going through the base station so that it attaches to the core network when it is determined that the communication module is in a detached state based on the communication status.

[0013] According to the above configuration, the communication method of the MTC device involves obtaining a communication status that allows determination of the attached and detached states of the communication module communicating with the core network via the base station, without going through the base station, and controlling the module to attach to the core network if it is determined to be in a detached state. Therefore, when a communication module is controlled to a detached state due to the influence of the communication environment within the cell, it is possible to control the communication module to attach to the core network. This makes it possible to suppress the loss of communication opportunities for the MTC device and improve the stability of communication quality in the MTC device.

[0014] Furthermore, it is preferable to control the operating state of the MTC device so that it transitions between a first operating state in which the MTC device operates with a first power energy and a second operating state in which the MTC device operates with a second power energy smaller than the first power energy; to cause the communication module to communicate with the core network in the first operating state; and to acquire the communication status in the second operating state. With the above configuration, the MTC device is controlled to transition between a first operating state in which it operates with a first power energy and a second operating state in which it operates with a second power energy smaller than the first power energy, and the communication status is acquired in the second operating state. Therefore, it is possible to monitor the attached and detached states of the communication module while suppressing the increase in power consumption associated with the monitoring.

[0015] According to the MTC device and the communication method for the MTC device of the present invention, it is possible to improve the stability of communication quality in machine communication.

[0016] This diagram illustrates the overview of the machine communication system. It shows the functional configuration of the MTC device. It also illustrates the transitions in the operating states of the MTC device. Finally, it shows the flow of the communication method for the MTC device.

[0017] Hereinafter, with reference to Figures 1 to 4, an MTC device 10 according to one embodiment of the present invention (hereinafter referred to as "this embodiment") and a communication method for the MTC device 10 will be described. However, the embodiments described below are merely examples to facilitate understanding of the present invention and do not limit the present invention. In other words, the present invention can be modified and improved without departing from its spirit, and of course, equivalents thereof are included in the present invention.

[0018] <<Overview of Machine Communication System 1>> Figure 1 is a diagram illustrating the overview of Machine Communication System 1. Machine Communication System 1 comprises an MTC device 10 that can communicate with the core network CN via a base station BS, and an MTC server 20 that collects data acquired by the MTC device 10, visualizes the collected data, and outputs it. The MTC device 10 and the MTC server 20 are connected via a publicly available cellular communication line CC. Alternatively, the MTC device 10 and the MTC server 20 may also be connected via the cellular communication line CC and an internet line (not shown). This enables the MTC device 10 and the MTC server 20 to perform wide-area communication.

[0019] The MTC device 10 is a communication device compliant with LTE-M (Long Term Evolution for Machines), a communication standard specifically for machine communication. The MTC device 10 may be attached to various devices and equipment to acquire and transmit information about the devices and equipment, or it may be attached to a mobile body such as an automobile to acquire and transmit information about the mobile body. As described later, the MTC device 10 has a sensor module 11 and a communication module 12 (see Figure 2), and wirelessly transmits data detected by the sensor module 11 to the MTC server 20 via the communication module 12 (uplink communication). Details of the MTC device 10 will be described later. The MTC device 10 corresponds to the MTC device of the present invention.

[0020] The MTC server 20 is a server device that has the function of collecting and storing data transmitted by the MTC device 10. The MTC server 20 is composed of one or more information processing devices. The MTC server 20 may also be an information processing device implemented as a cloud system. The MTC server 20 has the function of analyzing the data collected and stored from the MTC device 10, performing evaluation processing, visualizing the data, and providing it to other information communication terminals.

[0021] The cellular communication line CC is a communication line compliant with LTE-M and has base station BS and core network CN. Base station BS, also called "eNodeB" or "eNB," is a relay device installed for each of the many cells that divide the communication area. Base station BS is installed on steel towers erected in locations with good line of sight, on the rooftops of buildings and apartments, or on utility poles. Base station BS ensures a communication area that covers the cells by effectively combining omnidirectional antennas and multiple directional antennas.

[0022] In Figure 1, three base station BS are shown, but this represents multiple base station BS, and it goes without saying that many base station BS are connected to the core network CN. Also, in Figure 1, one MTC device 10 is connected to one base station BS, but this one MTC device 10 represents multiple MTC devices 10, and it goes without saying that many MTC devices may be connected within a cell.

[0023] The core network CN forms the core of the cellular communication line CC and includes a mobility management device CN1, a serving gateway CN2, and a packet data network gateway CN3.

[0024] The mobility management device CN1, also known as "MME," acts as a gateway for control signals. The mobility management device CN1 receives an attach request from the communication module 12 of the MTC device 10 via the base station BS and sends an attach response to the MTC device 10. This causes the MTC device 10 to transition to an attached state (online state) where it can communicate with the core network CN. The mobility management device CN1 also sends a detach request to the MTC device 10 depending on the communication environment within the cell. This causes the MTC device 10 to transition to a detached state (offline state) where it cannot communicate with the core network CN.

[0025] The serving gateway CN2, also known as "SGW," acts as a gateway for data packets transmitted and received by the MTC device 10. More specifically, the serving gateway CN2 relays data packets between the base station BS and the packet data network gateway CN3, which will be described later. The packet data network gateway CN3, also known as "PGW," acts as a gateway that relays data packets between the cellular communication line CC and external communication lines. To give a specific example, the packet data network gateway CN3 can relay communication packets between the cellular communication line CC and an internet line (not shown).

[0026] In the machine communication system 1 configured as described above, the MTC device 10 communicates wirelessly with the core network CN via the base station BS of the cellular communication line CC. Here, an upper limit is set on the number of MTC devices 10 that can communicate with the base station BS, and MTC devices 10 exceeding this limit cannot communicate wirelessly with the base station BS. Therefore, depending on the communication environment within the cell, the MTC device 10 may be controlled to a detached state in which it cannot communicate with the core network CN. In this embodiment, the MTC device 10 can monitor whether or not it has been controlled to a detached state and can return to an attached state based on the monitoring result. This makes it possible to suppress the loss of communication opportunities for the MTC device 10 in the detached state and to improve the stability of communication quality in machine communication.

[0027] <<MTC Device 10>> Next, the MTC device 10 will be described in detail. Figure 2 is a diagram showing the functional configuration of the MTC device 10. As shown in Figure 2, the MTC device 10 mainly consists of a sensor module 11, a communication module 12, a communication antenna 13, a power supply module 14, and a control module 15.

[0028] The sensor module 11 is responsible for detecting physical quantities at the installation location of the MTC device 10. More specifically, the sensor module 11 has a flow sensor 111 and a pressure sensor 112, and can detect the flow rate and pressure of a fluid. For example, when the MTC device 10 is attached to a water supply pump, the flow sensor 111 detects the amount of water supplied by the water supply pump, and the pressure sensor 112 detects the water supply pressure of the water supply pump. This makes it possible to remotely monitor whether the water supply pump motor is operating properly. However, the physical quantities detected by the sensor module 11 are not limited to flow rate and pressure. The sensor module 11 may also detect vibrations using an acceleration sensor. In addition, the sensor module 11 may also detect temperature using a temperature sensor.

[0029] The communication module 12 is a communication circuit compliant with LTE-M. More specifically, the communication module 12 is a wireless communication circuit that transmits data detected by the sensor module 11 to the MTC server 20 via the base station BS and the core network CN. The communication module 12 may also receive control data via the base station BS and the core network CN. The communication module 12 mainly consists of an RF circuit 121 and a communication control circuit 122.

[0030] The RF circuit 121 has a transmitting unit that includes a frequency conversion circuit, a filter circuit, and an amplification circuit, and generates a high-frequency signal that can be transmitted via the communication antenna 13. However, the RF circuit 121 may further have a receiving unit that acquires a baseband signal from the high-frequency signal received via the communication antenna 13.

[0031] The communication control circuit 122 controls the communication module 12 and manages the communication status. More specifically, the communication control circuit 122 stores communication status information that allows it to determine whether the communication module 12 is in an attached state or a detached state. The communication control circuit 122 is also connected to the control module 15, which will be described later, via multiple communication ports (first communication port 156 and second communication port 157). More specifically, the communication control circuit 122 can acquire control signals from the control module 15 via the first communication port 156 and control the RF circuit 121 to transmit high-frequency signals. The communication control circuit 122 can also output the communication status to the control module 15 via the second communication port 157.

[0032] The communication antenna 13 is an antenna that transmits the high-frequency signal output by the communication module 12. The communication antenna 13 is a chip antenna that can be miniaturized, but is not limited to this. It just needs to have antenna gain and directivity that allows communication with the base station BS, and the communication antenna 13 may be a patch antenna or a whip antenna.

[0033] The power module 14 supplies electrical energy to the sensor module 11, the communication module 12, and the control module 15. The power module 14 has, but is not limited to, a rechargeable secondary battery and a constant voltage output circuit (DC-DC converter). The power module 14 may also have a primary battery. Furthermore, the power module 14 may be equipped with a power receiving terminal that can receive electrical energy from an external source.

[0034] The control module 15 is a control circuit comprising a control processor 15a, a volatile memory, and a non-volatile memory, and is responsible for controlling the MTC device 10. The control module 15 functions as a detection data acquisition unit 151, a communication status acquisition unit 152, an attachment control unit 153, a status control unit 154, and a timing unit 155 by having the control processor 15a load a program stored in the non-volatile memory into the volatile memory and execute it.

[0035] The detection data acquisition unit 151 acquires detection data (flow rate data and pressure data) detected by the flow sensor 111 and the pressure sensor 112. The detection data acquisition unit 151 may also have an A / D converter and a filter circuit. Furthermore, the detection data acquisition unit 151 may include a calculation circuit for acquiring statistical values ​​(average value, maximum value, minimum value) of the detection data.

[0036] The communication status acquisition unit 152 communicates with the communication module 12 and acquires the communication status. The communication status is information that can determine the attached and detached states of the communication module 12, but is not limited to this. The communication status may also include the amount of communication and the communication time of the communication module 12. Furthermore, the communication status may include more detailed information regarding the communication state of the communication module 12. As described above, the control module 15 and the communication module 12 are connected to each other via the first communication port 156 and the second communication port 157. The first communication port 156 is used to transmit control data for communication control of the communication module 12 to the communication module 12. The first communication port 156 may also be used to transmit detection data acquired by the detection data acquisition unit 151 to the communication module 12.

[0037] The second communication port 157 is a dedicated communication port used to obtain the communication status of the communication module 12. By using the second communication port 157 to obtain the communication status, the communication status of the communication module 12 can be obtained regardless of the communication status of the first communication port 156. Furthermore, by using the second communication port 157, the communication status acquisition unit 152 can obtain the communication status without affecting the communication of the first communication port 156.

[0038] The second communication port 157 is preferably a communication port that supports a GPIO (General Purpose Input / Output) interface. This makes it possible to suppress the increase in power consumption associated with the acquisition of the communication status by the communication status acquisition unit 152, and also makes it possible to suppress the increase in the cost of the MTC device 10.

[0039] The attachment control unit 153 determines whether the communication module 12 is in a detached state based on the communication status, and controls the communication module 12 to attach to the core network CN if it is determined to be in a detached state. More specifically, the attachment control unit 153 causes the communication module 12 to send an attach request signal to the core network CN via the base station BS. After receiving an attach response signal transmitted from the core network CN, the communication module 12 transitions from the detached state to the attached state. This makes it possible to return the communication module 12 to the attached state even if it has been in a detached state. Therefore, it is possible to suppress the loss of communication opportunities for the MTC device 10 due to the communication module 12 being controlled to be in a detached state, and to improve the stability of communication quality.

[0040] The state control unit 154 controls the MTC device 10 to transition between a normal operating state and a sleep state at predetermined timings. Figure 3 is a diagram illustrating the transition of the operating states of the MTC device 10. As shown in Figure 3, the state control unit 154 controls the MTC device 10 to transition to a normal operating state with a first power consumption P1 between time T1 and time T2, and between time T3 and time T4. In the normal operating state, the flow sensor 111 of the sensor module 11 acquires flow data, and the pressure sensor 112 acquires pressure data. Also in the normal operating state, the communication module 12 converts the flow data and pressure data acquired by the sensor module 11 into high-frequency signals and transmits them via the communication antenna 13. The normal operating state corresponds to the first operating state of the present invention, and the first power consumption P1 corresponds to the first electrical energy.

[0041] Furthermore, the state control unit 154 controls the MTC device 10 to transition to a sleep state between time T2 and time T3, where it operates with a second power consumption P2 that is smaller than the first power consumption P1. In the sleep state, the flow sensor 111 and pressure sensor 112 of the sensor module 11 do not acquire flow data and pressure data. Also, in the sleep state, the communication module 12 does not transmit high-frequency signals. Therefore, the MTC device 10 transmits flow data and pressure data to the MTC server 20 in the normal operating state, while suppressing the consumption of unnecessary power energy in the sleep state. The sleep state corresponds to the second operating state of the present invention, and the second power consumption P2 corresponds to the second power energy.

[0042] The aforementioned communication status acquisition unit 152 acquires the communication status of the communication module 12 at time Ta in the sleep state. Then, if the attachment control unit 153 determines that the communication module 12 is in a detached state based on the communication status, it controls the communication module 12 to attach to the core network CN. The predetermined time Ta is a predetermined time before time T3 when the MTC device 10 transitions from the sleep state to the normal operation state, and at time T3, the MTC device 10 is able to obtain an opportunity to communicate with the core network CN.

[0043] The timing unit 155 includes a clock oscillator and a counter that counts the output of the clock oscillator. The clock oscillator is a crystal oscillator, but is not limited to it. The clock oscillator may also be a ceramic oscillator. The timing unit 155 outputs a timing signal when it is time for the communication status acquisition unit 152 to acquire the communication status. Specifically, when time Ta shown in Figure 3 arrives, the timing unit 155 outputs a timing signal to the communication status acquisition unit 152. The timing unit 155 also outputs a timing signal when it is time to transition from the sleep state to the normal operation state. Specifically, when time T1 and time T3 shown in Figure 3 arrive, the timing unit 155 outputs a timing signal to the state control unit 154.

[0044] <<Communication Processing of MTC Device 10>> Next, the communication processing of the MTC device 10 will be described. FIG. 4 shows the flow of communication processing executed by the control module 15 of the MTC device 10 at a predetermined timing (for example, a cycle of 100 msec). As shown in FIG. 4, the control module 15 first determines whether the state transition timing has arrived (step S10). More specifically, the control module 15 determines whether the timing unit 155 has output a timing signal indicating the arrival of the timing for transitioning from the sleep state to the normal operation state (the timings at times T1 and T3 in FIG. 3).

[0045] If it is determined that the state transition timing has arrived (step S10: Yes), the control module 15 transitions the MTC device 10 to the normal operation state (step S11). More specifically, the state control unit 154 causes the power energy output by the power module 14 to be supplied to the sensor module 11, the communication module 12, and the control module 15, thereby transitioning each module to an operable state.

[0046] Next, the control module 15 acquires detection data (step S12). More specifically, the flow rate sensor 111 of the sensor module 11 acquires flow rate data, and the pressure sensor 112 acquires pressure data. The flow rate data and the pressure data are acquired by the detection data acquisition unit 151 of the control module 15.

[0047] The detection data acquisition unit 151 may acquire statistical values of the flow rate data and the pressure data. More specifically, the detection data acquisition unit 151 may acquire the average value, the maximum value, and the minimum value of the data detected by the flow rate sensor 111 or the pressure sensor 112. Further, the detection data acquisition unit 151 may acquire the frequency parameters of the flow rate data and the pressure data. More specifically, the detection data acquisition unit 151 may acquire the peak frequency of the data detected by the flow rate sensor 111 or the pressure sensor 112. Also, the detection data acquisition unit 151 may determine the presence or absence of an abnormality based on the flow rate data and the pressure data, and acquire the determination result. More specifically, the detection data acquisition unit 151 may determine the presence or absence of an abnormality by comparing the data detected by the flow rate sensor 111 or the pressure sensor 112 with a predetermined abnormality determination threshold value, and acquire the determination result.

[0048] Next, the control module 15 transmits the detection data (step S13). More specifically, the control module 15 outputs the detection data acquired by the detection data acquisition unit 151 to the communication module 12, converts it into a high-frequency signal, and transmits it to the MTC server 20 via the communication antenna 13.

[0049] Next, the control module 15 transitions the MTC device 10 to the sleep state (step S14). More specifically, the state control unit 154 stops supplying power energy to the sensor module 11. Also, the state control unit 154 stops supplying power energy to the RF circuit 121. Further, the state control unit 154 may partially limit the supply of power energy to the control module 15. [[ID=⑧]]

[0050] [[ID=⑨]]Next, the control module 15 resets the time measurement by the time measurement unit 155 (step S15) and ends the communication process. More specifically, the time measurement unit 155 resets the count value of the counter that counts the output of the clock oscillator. [[ID=⑩]] [[ID=⑪]]

[0051] On the other hand, if it is not determined in step S10 that the state transition timing has arrived (step S10: No), the control module 15 determines whether or not the communication status acquisition timing has arrived (step S16). More specifically, the control module 15 determines whether or not the timing unit 155 has output a timing signal indicating the arrival of the timing for acquiring the communication status (the timing at time Ta in Figure 3). If it is not determined that the communication status acquisition timing has arrived (step S16: No), the control module 15 terminates the communication process.

[0052] On the other hand, if it is determined that the timing for acquiring the communication status has arrived (step S16: Yes), the control module 15 acquires the communication status (step S17). More specifically, the communication status acquisition unit 152 communicates with the communication control circuit 122 of the communication module 12 via the second communication port 157, which is a dedicated communication port, and acquires a communication status that allows determination of the attached state and detached state of the communication module 12.

[0053] Next, the control module 15 determines whether the communication module 12 is in a detached state or not (step S18). More specifically, the attachment control unit 153 determines whether the communication module 12 is in a detached state or not based on the communication status acquired by the communication status acquisition unit 152. If it is determined that the communication module 12 is not in a detached state (step S18: No), the control module 15 terminates the communication process.

[0054] On the other hand, if it is determined that the communication module 12 is in a detached state (step S18: Yes), the control module 15 executes the attachment process (step S19). More specifically, the attachment control unit 153 controls the communication module 12 to attach to the core network CN by having the communication module 12 send an attach request signal to the core network CN. Here, the attachment control unit 153 has the power supply module 14 supply power energy to the RF circuit 121 to transition the RF circuit 121 to an operational state before sending the attach request signal. When the communication module 12 receives an attach response signal from the core network CN, the attachment process ends, and the control module 15 terminates the communication process.

[0055] The above describes the flow of communication processing performed by the control module 15 of the MTC device 10. The MTC device 10 includes a communication module 12 that communicates with the core network CN, and a control module 15 that controls the communication module 12. The control module 15 acquires a communication status that allows determination of the attached state and detached state of the communication module 12, and controls the communication module 12 to attach to the core network CN when it is determined to be in a detached state based on the communication status. Furthermore, the communication method of the MTC device 10 performs the following actions: acquiring a communication status that allows determination of the attached state and detached state of the communication module 12, which can transition between the attached state and the detached state, without going through the base station BS, and controlling the communication module 12 to attach to the core network CN when it is determined to be in a detached state based on the communication status, without going through the base station BS. This makes it possible to suppress the loss of communication opportunities for the MTC device 10 and to improve the stability of the communication quality of machine communication performed by the MTC device 10.

[0056] We have described an MTC device 10 according to one embodiment of the present invention and a method for communicating with the MTC device. However, the above-described embodiment is merely an example to facilitate understanding of the present invention and does not limit it. That is, the present invention can be modified and improved without departing from its spirit, and of course, the present invention includes equivalents thereof.

[0057] In the embodiments described above, the communication status acquisition unit 152 was described as acquiring the communication status at a predetermined timing in the sleep state (the timing shown as time Ta in Figure 3), but the timing of acquiring the communication status is not limited to this. The communication status acquisition unit 152 may acquire the communication status at periodic timings in the sleep state. This makes it possible to return the communication module 12 to the attached state earlier when the communication module 12 becomes detached. Alternatively, the communication status acquisition unit 152 may acquire the communication status at the timing immediately after the MTC device 10 transitions to the normal operating state.

[0058] Furthermore, in the above-described embodiment, the attachment control unit 153 was described as transitioning the RF circuit 121 to an operational state before transmitting an attach request signal when it determined that the communication module 12 was in a detached state, but it is not limited to this. The attachment control unit 153 may also wait until the timing when the MTC device 10 transitions from a sleep state to a normal operating state when it is determined that the communication module 12 is in a detached state, and then transmit an attach request signal after it has transitioned to a normal operating state. This makes it possible to suppress the power consumption of the MTC device 10.

[0059] Furthermore, in the embodiments described above, the communication module 12 was described as transitioning between an attached state in which it can communicate with the core network CN and a detached state in which it cannot communicate with the core network CN. However, the communication states of the communication module 12 are not limited to these. The communication module 12 may have communication states other than the attached state and the detached state, and may transition between these states.

[0060] Furthermore, although the above-described embodiment assumed that the communication module 12 and the control module 15 are connected to each other via a dedicated port corresponding to the GPIO interface, the system is not limited to this. The communication module 12 and the control module 15 can monitor the attached and detached states of the communication module 12, and it is sufficient that the communication module 12 is connected in a way that allows it to be controlled to the attached state when it is in the detached state.

[0061] Furthermore, although the MTC device 10 was described as an LTE-M compliant communication device in the embodiments described above, it is not limited to this. The MTC device 10 may also be a communication device compliant with NB-IoT (Narrow Band-IoT) or mMTC (massive Machine Type Communication). Even in such cases, the same effects as in the embodiments described above can be achieved by the control module 15 monitoring the attached and detached states of the communication module 12 and controlling it to attach to the core network CN when it is detached.

[0062] Furthermore, in the embodiments described above, the MTC device 10 comprises a communication module 12 and a control module 15, and the control module 15 is described as monitoring the attached and detached states of the communication module 12. However, the invention is not limited to this. A control device, separate from the MTC device 10 and capable of sending control signals to the communication module 12, may acquire the communication status of the communication module 12 without going through the base station BS (for example, via a control cable). Then, if the communication module 12 is determined to be in a detached state based on the communication status, the control device may control the communication module 12 to attach to the core network CN without going through the base station BS. Even in such a case, the same effects as in the embodiments described above can be achieved. In this case, the control device controls the operating state so that the MTC device 10 transitions between a normal operating state in which it operates with a first power consumption P1 and a sleep state in which the MTC device 10 operates with a second power consumption P2 which is less than the first power consumption P1. The control device also performs the following: in the normal operating state, it communicates with the core network CN to the communication module 12, and in the sleep state, it acquires the communication status.

[0063] Furthermore, although the above-described embodiment assumed that the control module 15 is configured separately from the communication module 12, this is not the only possible configuration. The control module 15 and the communication module 12 may be implemented as a single integrated semiconductor circuit, or the communication module 12 may incorporate the functional configuration of the control module 15 described above. Even in such cases, the same effects as those of the above-described embodiment can be achieved.

[0064] 1 Machine Communication System 10 MTC Device (MTC Equipment) 11 Sensor Module 111 Flow Sensor 112 Pressure Sensor 12 Communication Module 121 RF Circuit 122 Communication Control Circuit 13 Communication Antenna 14 Power Module 15 Control Module 15a Control Processor 151 Detection Data Acquisition Unit 152 Communication Status Acquisition Unit 153 Attachment Control Unit 154 Status Control Unit 155 Timing Unit 156 First Communication Port 157 Second Communication Port 20 MTC Server CC Cellular Communication Line BS Base Station CN Core Network CN1 Mobility Management Device CN2 Serving Gateway CN3 Packet Data Network Gateway

Claims

1. An MTC (Machine Type Communication) device that performs wireless communication with a core network via a base station, comprising: a communication module that can transition between an attached state in which communication with the core network is possible and a detached state in which communication with the core network is impossible; and a control processor that controls the communication module, wherein the control processor acquires a communication status that can determine the attached state and the detached state of the communication module, and controls the communication module to attach to the core network when it is determined that the communication module is in a detached state based on the communication status.

2. The MTC device according to claim 1, characterized in that the control processor controls the MTC device to transition between a first operating state in which the MTC device operates with a first power energy and a second operating state in which the MTC device operates with a second power energy less than the first power energy, the communication module communicates with the core network in the first operating state, and the control processor acquires the communication status in the second operating state.

3. The MTC device according to claim 1, wherein the communication module and the control processor are connected to each other via a plurality of communication ports, and the control processor obtains the communication status from the communication module via a dedicated communication port among the plurality of communication ports.

4. The MTC device according to claim 3, characterized in that the dedicated communication port is a communication port compatible with a GPIO (General Purpose Input / Output) interface.

5. A communication method for an MTC (Machine Type Communication) device that performs wireless communication with a core network via a base station, comprising: acquiring a communication status that can determine the attached state and detached state of a communication module that can transition between an attached state in which communication with the core network is possible and a detached state in which communication with the core network is not possible, without going through the base station; and controlling the communication module, without going through the base station, to attach to the core network when the communication module is determined to be in a detached state based on the communication status.

6. A communication method for an MTC device according to claim 5, characterized by controlling the operating state of the MTC device so as to transition between a first operating state in which the MTC device operates with a first power energy and a second operating state in which the MTC device operates with a second power energy less than the first power energy; causing the communication module to communicate with the core network in the first operating state; and acquiring the communication status in the second operating state.

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